Here's my guideline.
The lip is there to catch the water, and both to give the bait a wiggle and to help it dive to a specific depth.
Wake baits, and shallow runner sit level in the water at rest, so they need the most angle for their lips, to catch the water when the retrieve is begun.
My wake baits have an 80+- degree angle off the centerline of the bait, as drawn from the front hook hanger to the rear hook hanger.
My 1.5 baits have a 35-40 degree angle.
If I want a bait to run deeper, I add more ballast at the belly hanger, and it hangs down more at rest, and the angle of the lip decreases, so it will still catch water and not just blow out. So I use about a 20 degree angle.
And my deep divers hang most nose down at rest, so I put the lip in more or less parallel with center line, at 0 degrees.
Every bait design will require some adjustments, but that is my starting point.
If you know what kind of bait you want to make, use a similar commercial bait as a stating point, and expand from there.